1. Field of the Invention
This invention relates to magnetic tape loading devices.
2. Description of the Prior Art
Video tape recorders (hereinafter referred to as "VTRs") have come into widespread use in recent years. As VTRs become more and more popular they find many applications and there are growing demands for smaller and lighter VTRs since users want VTRs that are more convenient to use and more immediately available for use. To meet such demands, attempts have been made to make VTRs smaller in size. Of the various components of the VTR, a head drum is one of the most important, being one of the largest and heaviest parts. Therefore, one way to produce a smaller VTR is to reduce the diameter of the head drum.
In conventional VTRs, a magnetic tape is wound on an arcuate surface of a head drum over a central angle of contact of about 180.degree.. A video signal indicative of one field is recorded over a predetermined length on each track, this length depending solely upon the head drum diameter and the angle of contact of the magnetic tape with the head drum. Accordingly, to make the head drum diameter smaller without any accompanying reduction of the length on the track, it is necessary that the angle of contact of the magnetic tape be substantially more than 180.degree.. A portable VTR of this kind, combined with a camera, has been disclosed by the assignees of the present application, for example in Published UK Patent Application No. GB 2,112,997 A and in Published EPC Application No. EP 0 102 811 A2, the disclosure of which are hereby incorporated herein by reference.
If the magnetic tape is to be wound on the head drum over the angle of contact of more than 180.degree.,a problem is experienced with a support means of the head drum and also with a loading mechanism for pulling out the magnetic tape from a tape cassette and winding the tape on the periphery of the head drum. More specifically, the loading mechanism has a tape guide portion for guiding the magnetic tape to wind it on the head drum, this tape guide portion being coupled with a drive mechanism through an elongate guide hole or slot formed (e.g. bored) in a chassis on which the head drum is supported. To allow the magnetic tape to be wound on the head drum at an angle of contact of more than 180.degree., such as more than 300.degree., the guide hole has to extend substantially fully around the head drum. A guide hole formed (e.g. bored) in this manner separates a portion of the chassis supporting the head drum thereon from the rest, so that the strength of the head drum supporting portion is reduced. Since the head drum is quite heavy and rotates at high speed, then when the drum supporting portion is separated from the rest of the chassis in this manner by the guide hole the head drum vibrates quite easily even when a small shock is imparted to the VTR, and causes an unfavorable displacement of the magnetic tape on the periphery of the head drum.
As well as the above-described problem of the low strength of the head drum supporting portion, it is difficult in the case of the conventional tape guide mechanism to wind the magnetic tape on the periphery of the head drum over an angle of contact of substantially more than 180.degree.. If this is attempted, the tape guide mechanism is rendered complex and a large space is required to move the tape guide mechanism. Therefore, it is scarcely possible in the case of the conventional tape guide mechanism to comply sufficiently with the demands for making the device smaller.